The overall organizing hypothesis of this Program posits that bioactive sphingolipids function as important regulators of several key tumor cell attributes, including tumor initiation, differentiation, growth, apoptosis, senescence, inflammation, invasion, and metastasis. As a corollary, enzymes of sphingolipid metabolism are emerging as specific and novel targets in modulating these important cancer attributes. Unfortunately, the study of bioactive lipids is rife with complications, both conceptual and technical and thus the study of lipids necessitates the collaborative interactions of various disciplines and specialized cores. Thus, we have evolved 4 distinct projects that collaborate to investigate the overall hypothesis. These projects address highly interrelated metabolic pathways that converge on the Golgi apparatus. Each project has identified a key node in these pathways that constitutes a specific vulnerability in the target cancer under study. Thus, Project 1 will test and advance the hypothesis that the novel acid sphingomyelinase/ceramide kinase pathway defines a previously unappreciated mechanism regulating invasiveness and metastasis of breast cancer. Project 2 will test the hypothesis that alkaline ceramidase 2 is a novel tumor suppressor whose suppression promotes development and progression of hepatocellular carcinoma. Project 3 will test the hypothesis that sphingosine kinase 1 (SK1) is a therapeutic target for p53 null and mutant cancers, and that Ser/Gly deprivation can be harnessed therapeutically to degrade SK1 and lead to cancer cell death. Project 4 will test the hypothesis that sphingomyelin synthase 1 is an indispensable novel regulator of proliferation of GATA1-positive AMLs (including the poorly studied acute erythroid, M6 and megakaryocytic, M7 leukemias) and a potential novel target for improving the dismal therapeutic response of these leukemias. These 4 projects will be supported by two unique research cores: The Lipidomics Shared Resource which will provide advanced analytical lipid chemistry and flux analysis, and by a Sphingolipid Animal Cancer Pathobiology Shared Resource that focuses on mutants/knock outs in enzymes of sphingolipid metabolism and models of in vivo carcinogenesis. It has recently introduced biobanking and CRISPR-mediated nock outs. This Program group has been highly integrated and productive (having published in the past 5 years 76 manuscripts, 50 of which were in collaboration) and has advanced significantly our understanding of sphingolipids (one of the last frontiers of basic research) in caner biology and therapeutics. We are now poised to advance pre-clinical studies and translational research based on our understanding of these novel pathways. These studies continue to identify novel targets and strategies for cancer therapeutics.